Anecdotal reports support the use of parenteral nutrition in cystic fibrosis (CF) patients. Controlled studies have not been reported. We previously studied parenteral nutrition/fat emulsion in 20 patients; a subgroup (4 patients) improved. These 4 differed in their serum lipid analyses from the other patients; the results suggested non-responding patients had a metabolic block which interfered with utilization of Intralipid. We are now comparing Intralipid with an experimental fat.